class User:
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.last_name = last_name

    def describe_user(self):
        print(f"first_name: {self.first_name}")
        print(f"last_name: {self.last_name}")

    def greet_user(self):
        print(f"Hello, {self.first_name} {self.last_name}!")
